Abdelaziz Fellah Carma Harding Language equations for timed alternating finite automata. 1075-1091 2003 80 Int. J. Comput. Math. 9 http://taylorandfrancis.metapress.com/openurl.asp?genre=article&issn=0020-7160&volume=80&issue=9&spage=1075 db/journals/ijcm/ijcm80.html#FellahH03